1. Field Of The Invention
This invention relates to a tool clamping mechanism for use in a tool engaging arm, such as the tool arm of a machining center or other machine tool, or of a robot arm.
2. Discussion Of The Prior Art
Tool changers for transferring cutting tools between a storage magazine and a machine tool spindle are well known in the machine tool arts. Typically, a tool changer comprises a tool change arm and some means for moving or successively positioning the arm as a tool change operation is performed. A tool change arm, in turn, typically includes a frame or support structure, and a clamping mechanism or like means mounted on the frame for grasping a tool to remove it from the magazine or spindle, and for solidly holding the tool as it is carried therebetween. Many different types of such grasping and clamping means have been tried in the past, involving complicated mechanisms which have been accident prone, expensive to manufacture, and subject to excessive failure.
Some prior clamping mechanism have relied upon a separate actuator for causing the mechanism to grasp the tool, after it has been moved into a tool engagement position. In addition to being complicated, these mechanisms have relied upon the actuator to remain energized during movement of the arm and tool between the magazine and spindle, in order to maintain tool clamping. In the event of a power failure or a failure of the actuator or a control component, it was possible that the mechanism could release, causing the tool to be dropped or thrown.
Many of the above and other clamping mechanisms would also execute clamping motion regardless of whether or not there was actually a tool in position to be clamped. Without a tool in position for clamping, the motion was both unnecessary and hazardous.